The present invention relates to an apparatus for launching one or more pigs into a subsea flowline or the like. More particularly, the invention relates to such an apparatus which utilizes the well fluid from a subsea christmas tree or the like, or the fluid from an external control and service line that is connected to the christmas tree, to launch the pigs from the device into the flowline.
In the field of subsea oil and gas production, pigs are used to, among other things, clean and inspect the flowline which connects one or more subsea christmas trees, manifolds or similar such sources of well fluid to a distant product receiving or production facility. The pigs are conveyed, or launched, into the flowline by a pig launcher, which typically comprises a cartridge for housing a number of pigs, a launch barrel for connecting the cartridge to the flowline, a source of fluid pressure for pushing the pigs from the cartridge into the flowline, and a number of launch valves to control the flow of fluid pressure from the fluid pressure source to the cartridge. Once the pig or pigs are launched into the flowline, they are conveyed to the product receiving or production facility by the flow of the well fluid from the subsea well.
Prior art pig launchers may be located at either the product receiving or production facility or adjacent the subsea well. When the pig launcher is located at the product receiving or production facility, a conduit must usually be provided between the that facility and the subsea well in order to convey the pigs from the pig launcher to the beginning of the flowline. When the pig launcher is located adjacent the subsea well, the fluid pressure source is typically still located at the product receiving or production facility, and a fluid pressure line must therefore be provided between that facility and the pig launcher. In addition, one or more control lines must also be provided between the product receiving or production facility and the pig launcher in order to convey control fluid to the launch valves. In either case, such conduits and lines extending from the facility to the subsea well or the pig launcher necessarily increase the cost and complexity of the subsea production system.
In accordance with the present invention, these and other limitations in the prior art are overcome by providing an apparatus for launching one or more pigs into a flowline which is fluidly connectable to a source of well fluid. The apparatus comprises at least one first hub to which the source of well fluid is connectable and which is in communication with the flowline, a first valve which is positioned between the first hub and the flowline, a second hub which is in communication with the flowline, and a pig launcher which is removably connectable to the second hub. The pig launcher includes at least one pig, at least one launch valve which is positioned between a pressure source and the pig, and a launch actuator for selectively opening and closing the launch valve. Furthermore, the launch actuator is controlled by a signal which is communicated through at least one of a number of external control and service lines that are connected to a control and service umbilical for the source of well fluid. In this manner, the control of the launch procedure is provided through the external control and service lines. Consequently, a separate controls umbilical from a production facility or the like is not required for the communication of control signals to the apparatus.
In accordance with one embodiment of the invention, the apparatus further comprises a fluid conduit which connects the first hub with the launch valve, and the pressure source comprises well fluid from the source of well fluid. Thus, a separate conduit from a production facility or the like is not required for the supply of pressurized fluid to the pig launcher.
In accordance with another embodiment of the invention, the apparatus further comprises means for fluidly connecting at least one of the external control and service lines with the launch valve, and the pressure source comprises fluid from the external control and service line. Consequently, neither well fluid nor a separate conduit from a production facility or the like are required for the supply of pressurized fluid to the pig launcher.
In one embodiment of the invention, the connecting means comprises a fluid connector which is mounted on the pig launcher and which is in fluid communication with the launch valve. In this manner, the external control and service lines may be connected directly to the pig launcher.
In another embodiment of the invention, the connecting means comprises a first fluid connector which is connectable to the external control and service line and which is fixed in position relative to the first and second hubs, a second fluid connector which is fixed in position relative to the first and second hubs, a number of control and service conduits which are connected between the first and second fluid connectors, and means for establishing fluid communication between the second fluid connector and the launch valve. The fluid communication means may include, for example, a third fluid connector which is fixed in position relative to the pig launcher and which is fluidly connected to the launch valve, and a fluid conduit which is connectable between the second and third fluid connectors. In this manner, the external control and service lines may first be connected to a support structure on which the first and second hubs are mounted, and then connected to the pig launcher via the second and third fluid connectors.
These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawings. In the drawings, the same reference numbers are used to denote similar components in the various embodiments.